1. The Field of the Invention
The present invention relates generally to heating systems, and is more particularly directed to a heating system capable of cooperatively capturing otherwise wasted heat of exhaust gases generated by a furnace.
2. The Known Art
Considerable attention and much discussion is being given to our national and world energy resources. Problems of fuel and power supply are now the concern of the home owner, the industry executive, as well as many of us who in the past have taken our heating and power supplies for granted. Perhaps a dividend of more recent energy crises has been the resulting reexamination of our energy reserves and the manner in which we presently use and waste energy. It is becoming increasingly obvious that a more efficient use of fuels will help to offset increases in fuel costs and will help to guarantee an unimpeded economic development for a long time to come. Conventional heating equipment has not escaped our scrutiny and it is this field that the present invention serves.
The technical literature is crowded with conventional heating and heat exchanging systems. Industrial heating furnaces, for example, are usually classified according to (1) the purpose for which the material is heated; (2) the nature of the transfer of heat to the material; (3) the method of firing the furnace; or (4) the method of handling material through the furnace. Home heating furnaces, on the other hand, are usually characterized by the fuel consumed and the medium being heated -- such as hot air, steam, hot water, etc.. Most furnaces or boilers generate a relatively hot exhaust medium which is ultimately conveyed to the environment or, in the case of more sophisticated systems, to recycling apparatus. In the case of hot exhaust gases, for example, a great deal of energy is wasted or not recaptured by the simple discharge of these gases at elevated temperatures into the atmosphere.
Conventional efforts to reclaim or recycle otherwise lost heat energy are best illustrated in equipment commonly referred to as economizers and air heaters. Economizers serve as traps for removing heating from flue gases and, as the name "economizer" implies, this type of unit is able to yield the user considerable savings in costs of fuel. Economizers are usually found in industrial applications in which they perform as feed water heaters which receive water from boiler feed pumps and deliver it at higher temperatures to steam-generating apparatus. In such conventional units, a forced-flow, convection heat-transfer arrangement consisting of a bank of steel tubes is supplied feed water at pressures greater than that of a generating section and at a rate commensurate with steam output of the system. Gas flow contacts the external surfaces of these tubes.
Air heaters, like economizers, function as traps to reclaim heat from flue gases, but usually make use of the air that is ultimately used for combustion. Air heaters, by reducing outlet gas temperatures to lower values than is possible with economizers supplied by heated feed water yield a gain in over-all thermal efficiency. These units are usually categorized as being either recuperative or regenerative types. However, both types depend upon a convection transfer of heat from a gas stream to a metal or other solid surface, followed by convection transfer from the solid to the cooling air.
Of course, there are many other types of heat exchangers known to the art which serve to reclaim what would otherwise be lost heat energy, many of which circulate mediums at different temperatures in close enough proximity to one another to permit an exchange of heat therebetween. However, such arrangements and equipment are usually costly to purchase and maintain, rather complex in their structural configuration, and not adaptable for use with both home as well as industrial heating systems.